Packers are installed in petroleum industry wellbores to isolate adjacent zones or regions from one another. Particularly, packers are used in petroleum production installations to isolate the annulus between a string of production tubing and a cased borehole to prevent the unwanted escape of production fluids.
Packers typically function by expanding one or more elastomeric packer elements to fill any gaps between the production tube (or a through bore of the packer) and the wellbore (either cased or open). The packer element can be expanded either by “inflating” the elastomeric elements with pressurized fluid or by upsetting flexible elements through axial compression. Additionally, packers may also include anchor devices to “bite” into the tubing or wellbore in which they are to be set. Slips of the anchor mechanism are often set and ratcheted in place to prevent the packer from displacing axially up or down the bore once it is set. Irrespective of construction or the deployment method used, packers effectively create fluid seals between an inner tubular member and an outer tubular member.
Furthermore, packers can be constructed to be either retrievable or permanent. Retrievable packers are preferably constructed so they can be set or retrieved into or out of a borehole with special tools and procedures. In contrast, permanent packers are not so easily retrieved. Because of their design and intent for long-term emplacement, most “permanent” packers must be destructively cut to release them from the location in which they are installed. This cutting operation typically severs mechanical devices that engage the bore to make the packer's engagement therewith permanent. Because slips of packer anchors are typically configured with one-way ratchet profiles, they cannot be easily released once engaged. As such, a cutting operation will be undertaken to cut and disengage the slips of the anchor mechanism so the packer assembly can be retrieved.
Currently, operations to remove a permanent packer or anchor involve running of a cutter assembly downhole to the location of the device to be cut. Next, a chemical or mechanical cutter head is activated and severs the critical components of the device to be released. The cutter assembly is then retrieved (leaving the crippled packer or anchor behind) so that a retrieving, or fishing, apparatus could be run into the hole to remove the severed packer assembly. Because a minimum of two trips downhole is required, an operation using this procedure can take considerable time and cause significant delays in downhole operations. Furthermore, because the cut packer is left in place while the cutter assembly is retrieved from and the fishing assembly is run into the hole, there is a chance the packer can fall deeper into the wellbore. As such, it is desirable that the cutting operations to retrieve packers and other anchor components to run as quickly as possible. Any apparatus or methods to improve cutting and retrieval operations for anchored downhole components would be well received in the industry.